In drilling and operating wells for oil and gas production, fluids and fluid additives are used for numerous different purposes. For example, during the initial drilling, fluids may be used for lubrication of the drilling string and drilling fluid additives may serve to increase lubricity or serve as “loss circulation materials” that serve to plug fissures in the geologic formation, thus inhibiting the loss of the drilling fluid into the formation. In such circumstances, it is known to add resilient materials to the drilling fluid. See, e.g., U.S. Pat. No. 5,826,669, which discloses a method of preventing or controlling the loss of well drilling fluid into the pores and fractures of subterranean rock formations by the addition of resilient graphitic carbon particles.
During well completion, necessary to bring the well into production once the drilling operations have been completed, the downhole casing string is assembled, and the annulus between the casing and the borehole is sealed with cement (“primary cementing”). After completion of the primary cementing operations, production of oil or gas may commence. As oil and gas flow through the wellbore, heat passes through the casing into the annular space, resulting in the expansion of any fluids therein. This may result in annular pressure build-up (“APB”), a potentially dangerous condition that could result in the rupture of the casing wall or production tubing. Techniques for mitigating APB include the introduction of resilient or elastic particles into the annulus that collapse when subjected to the high pressures of APB, thus increasing the available volume of the annulus and decreasing the pressure. See, e.g., U.S. Pat. No. 8,080,498, which discloses the use of elastic hollow particles that buckle at or near a defined pressure and rebound towards their original shape as the pressure decreases for mitigating APB.
By way of the present disclosure a compressible carbonaceous particulate material is provided that has highly repeatable contraction and expansion characteristics (“reversible volumetric contraction and expansion”) when subjected to extremely high temperatures and pressures, such that the material reversibly expands and contracts by about 20% when subjected to pressures of up to 10,000 psi. This is believed to be due to the abundant fine closed porosity within the resilient structure of the particulate material, as evidenced by the fact that the milling of the material to a desired particle size distribution has a minimal effect on the true density of the milled material versus that of the starting material. Accordingly, the material can be added to increase the compressibility of fluid and solid mixtures, and may be suitable for adding to drilling fluids as, e.g., an LCM, wellbore service fluids to, e.g., mitigate APB, and cement slurries, for primary cementing or otherwise.